Air dehumidification unit and process

ABSTRACT

An air dehumidification unit of a heating, ventilating, and air conditioning system includes an air flow channel configured to guide a flow of air through an evaporator disposed therein, and a drainage channel coupled to the air flow channel. The drainage channel has an internal volume configured to receive a fluid condensed at the evaporator from the flow of air. The air dehumidification unit further includes a heating device configured to heat the internal volume of the drainage channel from outside of the internal volume of the drainage channel to militate against a formation of ice therein. The invention also relates to a method for dehumidifying the air in the heating, ventilating, and air conditioning system of a motor vehicle using the air dehumidification unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of German Patent Application No. DE 10 2011 053 906.9 filed Sep. 23, 2011, the entire disclosure of which is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to an air dehumidification unit for an HVAC system of a motor vehicle and, more particularly to an air dehumidification unit for an HVAC system of a motor vehicle which is capable of combined refrigeration system and heat pump operation. Further, the invention relates to a process for dehumidifying air to be conditioned of a passenger compartment in the HVAC system operated as a heat pump using the air dehumidification unit.

BACKGROUND OF THE INVENTION

Typically, a heating, ventilating, and air conditioning (HVAC) system is used at ambient temperatures above 0° C. In hybrid and electric vehicles efficient heating is necessary. As such, heat pump systems have been developed. For efficiency, refrigerant circuits of the heat pump systems are operated in an air recirculation mode or a partial air recirculation mode at cold ambient temperatures requiring air dehumidification before reheating the air, especially in transitional periods between seasons.

From DE 101 63 607 A1, an HVAC system for a motor vehicle is known. The HVAC system is provided with an integrated heat pump for cooling and heating a passenger compartment of the vehicle. A refrigerant is circulated in a circuit which enables heat transfer to a supply air for the passenger compartment of the vehicle. Heat directly enters into an air flow for the passenger compartment using the integrated heat pump.

DE 10 2006 026 359 A1 discloses problems associated with heat pump systems. One such problem is that, oftentimes, the heat pump systems cannot dehumidify and heat the air to be supplied to a passenger compartment of the vehicle at the same time. As such, the HVAC system of the vehicle cannot be operated using recirculated air from the passenger compartment. Due to a lack of the dehumidification of the air, an undesired fogging of window glass occurs.

In DE 10 2006 026 359 A1, an HVAC system for combined refrigeration and heat pump operation for vehicles with a primary circuit and a secondary passage is described. The primary circuit includes components known from a typical compression refrigeration system such as a compressor, a first gas cooler for heat transfer from a refrigerant to an environment, a throttling member, and an evaporator for cooling air to be supplied to a passenger compartment. The secondary passage has a first section and a second section. The first section, which originates from a branching point placed between the compressor and the first gas cooler, extends up to an entering point placed between the first gas cooler and the compressor. The first section includes a second gas cooler for heat transfer from the refrigerant to the air of the passenger compartment to be heated and a subsequent second throttling member. The second section of the secondary passage, which originates from another branching point placed between the second gas cooler and the compressor, extends up to another entering point placed between the second gas cooler and the compressor. In a heat pump operation, the refrigerant passes the first section and the second section of the secondary passage, as well as the primary circuit of the HVAC system. For heating the air supplied to the passenger compartment, the refrigerant is compressed in the compressor and then flows through the first section of the secondary passage to the second gas cooler via an active switching valve. In the second gas cooler, as opposed to the first gas cooler, the heat from the refrigerant is not dissipated to the environment, but used to heat the air of the passenger compartment. In the second throttling member, subsequent to the second gas cooler, the refrigerant is expanded from the compression pressure level to a mean pressure level to produce a two-phase mixture. By means of the mean pressure level, a refrigerant-side temperature level in the evaporator is controlled. In cases of an air temperature of above 0° C. before the evaporator, the temperature level in the evaporator must not be decreased to below 0° C. in order to prevent the evaporator from icing. On the other hand, the temperature level in the evaporator must not be above 0° C. to avoid sudden fogging of the window glass in case of an air temperature of below 0° C. before the evaporator. in the evaporator, a portion of the refrigerant is evaporated, whereby the air supplied to the passenger compartment is cooled and dehumidified. Upon dehumidification, the water contained as air humidity in the supplied air condenses at the evaporator. The resulting water condensate must be removed from the HVAC system at all temperature conditions, particularly at temperatures below 0° C. Hereby, however, the water condensate in a water drainage channel provided to remove the water condensate may freeze, obstructing an outflow of the water condensate.

A de-icing of water condensate drainage hoses is known from JP 08040052 A. Generally, an HVAC system is provided with a drainage hose having a section mounted to a motor vehicle body, connected to a cooling unit, whereas another section is opened such that condensed water from the cooling unit can flow off to the exterior. Specifically, a drainage hose structure of the cooling unit is described that is provided with a drainage hose and a heating element placed on an inner wall of the drainage hose. The drainage hose can be heated by the heating element from an interior when the condensed water reaches a freezing temperature. Disadvantageously, the drainage hose has a narrowed diameter and a minimized internal volume due to the heating device. Moreover, the heating device only covers part of the inner wall of the hose so that the inner wall is not homogeneously heated.

It is the objective of the invention to produce an HVAC system of a motor vehicle configured for combined refrigeration system and heat pump operation, which includes an air dehumidification unit for air to be supplied to a passenger compartment of the motor vehicle, that at all temperature conditions and in all ventilation modes ensures sufficient dehumidification of the supplied air. Particularly, the air dehumidification unit is intended to be suitable for a corresponding HVAC system that allows heating of the air for the passenger compartment also at a high recirculation air portion at an ambient temperature of below −10° C. in the heat pump operation without a fogging of the window glass.

SUMMARY OF THE INVENTION

In concordance and agreement with the present disclosure, an HVAC system of a motor vehicle configured for combined refrigeration system and heat pump operation, which includes an air dehumidification unit for air to be supplied to a passenger compartment of the motor vehicle, that at all temperature conditions and in all ventilation modes ensures sufficient dehumidification of the supplied air, is surprisingly discovered.

The problem of the invention is solved by an air dehumidification unit of a motor vehicle HVAC system for a combined refrigeration system and heat pump operation, wherein the motor vehicle HVAC system comprises a heat pump system with a refrigerant-based heating heat exchanger and an evaporator for supplying heat from air to be conditioned for an interior of the motor vehicle to the refrigerant passed in a circuit, wherein the air dehumidification unit includes the following components:

-   -   an air flow channel, in that the evaporator is located, for         passing the air to be conditioned over the evaporator;     -   a vertically oriented condensate water drainage channel         branching off at a bottom side of the air flow channel for         removing water condensed at the evaporator from the air to be         conditioned; and     -   a heating device that either is integrated into a wall of the         condensate water drainage channel or is placed outside the         condensate water drainage channel adjacent the condensate water         drainage channel such that the heating device is capable to heat         the internal volume of the condensate water drainage channel         from the exterior.

In an embodiment of the invention the heating device is a heating wire with a positive temperature coefficient (PTC) integrated into the wall of the condensate water drainage channel.

Particularly, the heating device is configured as an electrical resistance heater with one or more heating resistors, integrated into the wall of the condensate water drainage channel. Preferably, heating resistors with positive temperature coefficient (PIC) are used.

Advantageously, the heating device is configured as electrical fiber elements with positive temperature coefficient (PTC) integrated into the wall of the condensate water drainage channel. Here, the condensate water drainage channel is preferably a hose formed from a plastic material with the electrical fiber elements woven into the hose or integrated into the hose by a molding process.

According to a preferred embodiment of the invention, the heating device is connected to a control or regulating device that enables operating the heating device dependent upon the ambient temperature over a constant heating mode or a mode controlled by an external signal.

In an alternative embodiment of the invention, the high pressure heat pump line of the heat pump system is located in an immediate vicinity of the condensate water drainage channel of the HVAC system so that the high pressure heat pump line serves as the heating device.

Another aspect of the invention is a process for dehumidifying air to be conditioned of a vehicle interior in a motor vehicle HVAC system operated as heat pump by means of an air dehumidification unit according to one of the above mentioned embodiments, wherein:

-   -   the air to be conditioned passes the evaporator along the air         flow channel;     -   the air to be conditioned hereby is cooled, and water contained         as air humidity condenses at the evaporator and flows off into         the condensate water drainage channel; and     -   when the ambient temperature falls below 0° C., the preferably         electrical heating device is operated in a constant heating mode         or a heating mode controlled by an external signal.

The heating device can be operated with interruptions. In an embodiment of the invention, the condensate water drainage channel is directly heated by the heating device, and frozen condensate is melted. An advantage of the air dehumidification unit according to the invention is that the condensate water drainage channel is heated through directly using the heating device at the periphery of the condensate water drainage channel. The frozen condensate is melted at the walls of the drainage channel, thus from the outside.

Alternatively, the heating device is used indirectly. Indirect use of the heating device keeps the temperature of the condensate above 0° C. In case of indirect use of the heating device, consumption of electric power can be minimized and freezing in the condensate water drainage pipe is militated against.

Preferably, the heating device is operated in function of the ambient temperature over a constant heating mode or over a mode controlled by an external signal. The external signal is advantageously dependent upon ambient temperature measured values and/or the recirculating air damper door position and/or humidity measurements.

In one embodiment, an air dehumidification unit of a heating, ventilating, and air conditioning system, comprises: an air flow channel configured to guide a flow of air through an evaporator disposed therein; a drainage channel coupled to the air flow channel, the drainage channel having an internal volume configured to receive a fluid condensed at the evaporator from the flow of air; and a heating device configured to heat the internal volume of the drainage channel from outside of the internal volume of the drainage channel.

The invention also relates to a method for dehumidifying air in a heating, ventilating, and air conditioning system of a motor vehicle.

The method comprises the steps of: providing an air dehumidification unit including an evaporator disposed in an air flow channel and a drainage channel having an internal volume coupled to the air flow channel; facilitating a flow of air through the air dehumidification unit which causes humidity in the flow of air through the air dehumidification unit to condense at the evaporator and a fluid to flow into the drainage channel; and heating an internal volume of the drainage channel from outside of the internal volume of the drainage channel.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present disclosure, will become readily apparent to those skilled in the art from the following detailed description, particularly when considered in light of the drawing described hereafter.

The drawing is schematic cross-sectional view of a HVAC system including an air dehumidification unit according to the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

The following detailed description and appended drawings describe and illustrate various embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner.

The drawing shows a section of an HVAC system of a motor vehicle with an air dehumidification unit 1 in a region of an evaporator 2, which serves to supply heat from air to be conditioned 3.1 of an interior of the vehicle to a refrigerant of a heat pump system. The evaporator 2 is located in an air flow channel 4 such that inflowing fresh air 3.1 or recirculating air 3.1 must pass through the evaporator 2. The air to be conditioned 3.1 passes through the evaporator 2 at a temperature of 15° C. and a relative air humidity of 80%, for example. After having passed through the evaporator 2, the dehumidified air has a relative air humidity of 97% and a temperature of 3° C., for example. In a region of the air flow channel 4 downstream of the evaporator 2, a vertically-oriented condensate water drainage channel 5 is located so that liquid water condensate 6.1 can flow downwards into the condensate water drainage channel 5. The condensate water drainage channel 5 is provided for drainage of the HVAC system. As illustrated in the drawings, the condensate water drainage channel 5—switched downstream in direction of flow of the air 3—is placed behind the evaporator 2 and oriented vertically to the air flow channel 4 in respect to a direction of flow of the supplied air 3. A guiding element 7, extending from a front edge of a bottom side of the evaporator 2 up to an inlet of the condensate water drainage channel 5, forms an inclined plane which ensures that the water condensate 6.1 condensed at the evaporator 2 flows down at an angle into the condensate water drainage channel 5.

At ambient temperatures of <0° C. portions 6.2 of the water condensate removed from a drying process can freeze.

The air dehumidification unit 1 is provided with a heating device 8 that, as shown in the drawing, either is integrated into a channel wall 9 of the condensate water drainage channel 5 or is placed outside the condensate water drainage channel 5 adjacent the condensate water drainage channel 5. Therefore, the heating device 8 is capable of heating an internal volume 10 of the condensate water drainage channel 5 from the outside.

The heating device 8 shown in the drawing can be configured as an electrical heating wire 8 with positive temperature coefficient (PTC) integrated into the channel wall 9 of the condensate water drainage channel 5. In another embodiment, the heating device 8 is configured as an electrical resistance heater 8 integrated into the channel wall 9, with one or more heating resistors. Also, in yet another embodiment, the heating device 8 can be configured as electrical fiber elements 8 with positive temperature coefficient (PTC) integrated into the channel wall 9 of the condensate water drainage channel 5. Preferably, the condensate water drainage channel 5 is a hose 5 formed from a plastic material with the electrical fiber elements 8 woven into the hose 5 or integrated into the hose 5 by a molding process.

While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the disclosure, which is further described in the following appended claims.

NOMENCLATURE

1 dehumidification unit

2 Evaporator

3 Air

3.1 air to be conditioned, inflowing fresh air/recirculating air

3.2 dehumidified air

4 air flow channel

5 condensate water drainage channel, hose

6.1 water, condensed water, condensate water

6.2 portions of the condensate water (already iced)

7 guiding element

8 heating device, electrical fiber elements, heating wire, resistance heater

9 channel wall

10 internal volume of the condensate water drainage channel 5 

What is claimed is:
 1. An air dehumidification unit of a heating, ventilating, and air conditioning system, comprising: an air flow channel configured to guide a flow of air through an evaporator disposed therein; a drainage channel coupled to the air flow channel, the drainage channel having an internal volume configured to receive a fluid condensed at the evaporator from the flow of air; and a heating device configured to heat the internal volume of the drainage channel from outside of the internal volume of the drainage channel.
 2. The air dehumidification unit of claim 1, wherein the drainage channel is substantially vertically oriented.
 3. The air dehumidification unit of claim 1, wherein the drainage channel is formed to extend laterally outwardly from a bottom portion of the air flow channel.
 4. The air dehumidification unit of claim 1, wherein the drainage channel is formed downstream of the evaporator in the air flow channel.
 5. The air dehumidification unit of claim 1, further comprising a guiding element extending from an upstream edge in respect of the flow of air of the evaporator to an inlet of the drainage channel.
 6. The air dehumidification unit of claim 5, wherein the guiding element forms an inclined plane which facilitates a flow of the fluid into the inlet of the drainage channel.
 7. The air dehumidification unit of claim 1, wherein the heating device is integrated into a wall which defines the internal volume of the drainage channel.
 8. The air dehumidification unit of claim 1, wherein the heating device is disposed adjacent the drainage channel.
 9. The air dehumidification unit of claim 1, wherein the heating device is an electrical heating wire with a positive temperature coefficient.
 10. The air dehumidification unit of claim 1, wherein the heating device is an electrical resistance heater with at least one heating resistor.
 11. The air dehumidification unit of claim 1, wherein the heating device is at least one electrical fiber element with a positive temperature coefficient.
 12. The air dehumidification unit of claim 11, wherein the at least one electrical fiber element with the positive temperature coefficient is at least one of woven and molded into the drainage channel.
 13. The air dehumidification unit of claim 1, wherein the drainage channel is a hose formed from a plastic material.
 14. The air dehumidification unit of claim 1, wherein the heating device is connected to at least one of a control device and a regulating device that enables operation of the heating device in one of a constant heating mode and a heating mode controlled by an external signal.
 15. The air dehumidification unit of claim 1, wherein the heating device is a high pressure heat pump line of a heat pump system disposed adjacent the drainage channel.
 16. A method for dehumidifying air in a heating, ventilating, and air conditioning system of a motor vehicle, comprising the steps of: providing an air dehumidification unit including an evaporator disposed in an air flow channel and a drainage channel having an internal volume coupled to the air flow channel; facilitating a flow of air through the air dehumidification unit which causes humidity in the flow of air through the air dehumidification unit to condense at the evaporator and a fluid to flow into the drainage channel; and heating an internal volume of the drainage channel from outside of the internal volume of the drainage channel.
 17. The method of claim 16, wherein the heating device is operated in one of a constant heating mode and a heating mode controlled by an external signal.
 18. The method of claim 17, wherein the external signal depends upon at least one of at least one measured value of an ambient temperature, a position of a recirculating air damper door, and at least one measurement of the humidity.
 19. The method of claim 16, wherein a direct heating of the drainage channel is performed when at least a portion of the internal volume of the drainage channel includes ice formed therein.
 20. The method of claim 16, wherein an indirect heating of the drainage channel is performed to minimize electric power consumption and militate against a formation of ice in the drainage channel. 